Greenpeace said its challenge to Shell's drilling plans for the Beaufort and Chukchi Seas was overturned by an Alaskan judge, who ruled the drilling campaign did not violate environmental laws.
The U.S. government in January ordered a review of the 2012 drilling program enacted by Shell in the Beaufort and Chukchi seas.
Shell equipment issues off the Alaskan coast last year raised concerns about the safety of arctic exploration.
"A first step would be to keep Shell out of the arctic," Greenpeace said in a statement. "Safe oil drilling in the far north is an oxymoron."
Greenpeace said it was concerned about the ability of Shell to respond to an oil spill in arctic waters. It said the approval for Shell sends a signal that protecting the pristine northern environment is not a priority for regulators.
"Greenpeace won't stop until Shell is out of the icy north and this special place is properly protected," it said.
The U.S. Court of Appeals for the District of Columbia in March said Greenpeace needs to end its campaign of interfering with Shell's work off Alaska.